Carboplatin analogs for cancer treatment

ABSTRACT

The synthesis and the use of a series of carboplatin analogs is disclosed. These carboplatin analogs may be represented by cis-Pt(II)L1L2, wherein each of L1 and L2, independently, is the carboxylate of phosphatidylserine, an alpha-amino acid, beta-amino acid, or a derivative thereof, wherein each ligand is bidentate with -NH2 and -COO- as the binding sites. The complexes can be used in the treatment of cancer.

This application is a division of application Ser. No. 09/552,167, filedApr. 18, 2000, (pending), which is hereby incorporated by referenceherein.

This application claims priority under 35 U.S.C. §119(e) to U.S.Provisional Patent Application Serial No. 60/130,530 filed Apr. 21,1999.

BACKGROUND OF THE INVENTION

This invention relates to the synthesis of a series of carboplatinanalogs which can be reversibly activated and deactivated and the use ofthese carboplatin analogs to treat cancer.

Cisplatin (cis-diaminedichloroplatinum, cis-Pt(NH₃)₂Cl₂) was the firstanticancer platinum drug. It has been used as a chemotherapeutic agentfor many years since the discovery of its anti-tumor activity by B.Rosenberg et. al. (Nature, 1965, 205: 698; Nature, 1972, 222: 385).

Chemical & Engineering News (Oct. 23, 1995) reported that “Cisplatin wasfirst synthesized in the 1800s, but its anticancer activity was notdiscovered until the 1960s. In 1979, it was approved by the Food andDrug Administration for clinical treatment of testicular and ovariantumors and cancers of the head and neck. Cisplatin and an analog,carboplatin, are now among the most widely used anticancer drugs.”

The Physician's Desk Reference (PDR) reports that cisplatin (thecommercial name is Platinol®) can be used to treat testicular cancer,ovarian cancer, and bladder cancer. Rosenberg et al., U.S. Pat. No.4,177,263, describes methods of treating cancer using cisplatin andcisplatin analogs. The compound was shown to be effective for treatingleukemia and tumors induced in mice.

After so many years, cisplatin is still being widely used because of itsefficacy. However, its critical drawback, the toxicity, is still a majorconcern.

Many people have attempted to change the ligand on platinum to makecisplatin analogs in order to reduce the toxicity or improve theefficacy. Examples are made by K. C. Tsou, et al. (J. Clin. Hemat.Oncol., 7: 322 (1977)); R. J. Speeder et al. (J. Clin. Hemat. Oncol., 7:210 (1977)); A. Mathew et al. (Chem. Comm., 222 (1979)); D. Rose, et al.(Cancer Treatment Reviews, 12: 1 (1985)); and D. Alberts et al. (CancerTreatment Reviews, 12, 83 (1985)).

In recent years, another platinum drug, carboplatin (Paraplatin®), hasbeen widely prescribed. As a cisplatin analog, carboplatin is becomingmore popular than cisplatin because it has a better therapeutic index.In other words, carboplatin has a better efficacy/toxicity ratio whenused in the treatment of cancer. Nevertheless, carboplatin still hassignificant side effects and it has been used only to certain cancers.Therefore, there is a need to further improve carboplatin to make itless toxic or more versatile.

BRIEF SUMMARY OF THE INVENTION

This invention comprises the synthesis of a series of platinum(II)complexes as carboplatin analogs for the treatment of cancer. Theseplatinum(II) complexes can be reversibly activated/deactivated in mediawith different pH values. These platinum(II) complexes can have asignificantly reduced drug resistance. Because the ligands are abundantbiologically, the drug resistance can be less than that of cisplatin orcarboplatin. In addition, they can be used in treating cancers that arenot treated by cisplatin or carboplatin because of the variety of theligands.

Other objects, features, and advantages of the present invention willbecome apparent from the following detailed description. It should beunderstood that the detailed description and the specific examples,while indicating preferred embodiments of the invention, are given byway of illustration only, since various changes and modifications withinthe spirit and scope of the invention will become apparent to thoseskilled in the art from this detailed description.

DETAILED DESCRIPTION OF THE INVENTION

One aspect of this invention is to significantly improve the performanceof platinum drugs. Thus, a series of platinum(II) complexes arepresented herein as carboplatin analogs. The platinum(II) complexes ofthis invention are similar to carboplatin in that each complex has twoactive sites individually protected by carboxylate groups. However,because each carboxylate group is part of the respective bidentateligand, hydrolysis of the carboxylate only separates it from the Pt(II)ion, but not the molecule. Therefore, both carboxylate groups are ableto reattach to Pt(II) under a higher pH condition, such as the normalbiological condition. This behavior makes the complexes significantlydifferent from carboplatin, in which carboxylate groups, whenhydrolyzed, are permanently separated from the Pt(II) ion. As a result,these platinum(II) complexes can be much less toxic than other platinumdrugs.

Another aspect of the present invention is to reduce the drug resistanceafter repeated treatment that is often seen with cisplatin orcarboplatin treatment. Unlike carboplatin, the platinum(II) complexes ofthis invention utilize the carboxylate of phosphatidylserine, α-aminoacids, β-amino acids, or their derivatives as the ligands. Because theplatinum(II) is camouflaged by these ligands, which are abundant inliving organisms, these complexes are much less likely to incur drugresistance on repeated treatment. Therefore, the carboplatin analogs ofthis invention have advantages over cisplatin or carboplatin.

Yet another aspect of the present invention is to expand the number andthe types of cancer in which the complexes can be effectively used.Cisplatin and carboplatin have been used only in some cancers, such astesticular and ovarian tumors, cancers of the head and neck, etc. Itwould be greatly beneficial to expand the use of platinum drugs to treatcancers that are not being treated by cisplatin and carboplatin.

The platinum(II) complexes of the present invention can havesignificantly different physical properties (such as solubility,affinity, permeability, stereo effect, etc.) from those of cisplatin orcarboplatin because of the variety of ligands that can be used andbecause of the ability of amino acids to induce and stabilize somelimited conformation themselves or when incorporated into smallpeptides. Therefore, these complexes can be useful in treating cancersthat are not treated by cisplatin or carboplatin.

Therefore, the platinum(II) complexes of this invention have severaldistinct advantages over carboplatin including (1) they can bereversibly activated and deactivated, (2) they can have a significantlyreduced drug resistance, and (3) they can be used to treat cancers thatare not treated by cisplatin or carboplatin.

Platinum(II) Complexes of the Present Invention

The complexes of the present invention can be represented bycis-Pt(II)L¹L², wherein each of L¹ and L², independently is thecarboxylate of phosphatidylserine, an α-amino acid, a β-amino acid, or aderivative thereof, wherein each ligand bidentate with —NH₂ and —COO⁻ asthe binding sites.

The following structure represents cis-Pt(valine)₂:

Suitable acid, such as HCl, HBr, or HNO₃, can be added to the complexesto make the free acid form, cis-Pt(II)Cl₂L¹L², cis-Pt(II)Br₂L¹L² orcis-Pt(II)(NO₃)₂L¹L² wherein each ligand is monodentate with —NH₂ as thebinding site. The structure Of PtCl₂(Valine)₂ is shown as an example:

The α-amino acid, β-amino acid, or derivative thereof, includes but isnot limited to, alanine, aspartic acid, glutamic acid, glycine,isoleucine, leucine, phenylalanine, proline, serine, threonine,tyrosine, and valine.

Similar to carboplatin, the platinum(II) complexes of the presentinvention are more likely to be hydrolyzed in a cancerous area where thepH is lower than the normal biological pH. Thus, the two platinum(II)active sites are exposed to interact with DNA. In contrast tocarboplatin, the active sites of the platinum(II) complex in thisinvention can be re-protected when they enter into a non-cancerous areabecause of the higher pH value. The activation/deactivation process forthe platinum(II) complex is reversible. Therefore, potential sideeffects can be significantly reduced.

The reversible activation/deactivation reaction of the complexes of thisinvention may be illustrated by the example below:

Whereas for carboplatin, it is a one-way reaction as illustrated below:

Therefore, these platinum(II) complexes or their free acids can be usedin treating cancer, and the platinum(II) complexes of the presentinvention are expected to have better therapeutic indices thancarboplatin and cisplatin.

Another advantage of these platinum(II) complexes is that theplatinum(II) ion is camouflaged by amino acids, which are abundant inliving organisms. This fact makes it much less likely to incur drugresistance. Drug resistance for anticancer drugs (such as cisplatin andcarboplatin) is well known for repeated treatment.

Yet another advantage of these platinum(II) complexes is that they canbe used to treat those cancers that are not treated by cisplatin orcarboplatin. This is because of the variety of ligands on thesecomplexes, which covers a wide range of physical/chemical properties,such as solubility, permeability, ionic charge, etc. Therefore, some ofthese complexes can be used to treat certain cancers while others can beused to treat other cancers. In other words, these complexes can be usedto treat a much broader range of various types of cancers.

Pharmaceuticals and Methods of Treating Cancer

In one aspect, the present invention provides methods for the treatmentof various malignancies. Treatment methods involve treating anindividual with an effective amount of the platinum(II) complexes ofthis invention, as described herein. An effective amount is defined,generally, as that amount sufficient to detectably and repeatedlyameliorate, reduce, minimize, or limit the extent of a disease or itssymptoms. More rigorous definitions may apply, including elimination,eradication or cure of disease.

To kill cells, inhibit cell growth, inhibit metastasis, decrease tumorsize, and otherwise reverse or reduce the malignant phenotype of tumorcells, using the methods and compositions of the present invention, onewould generally contact a “target” cell with the platinum(II) complexesof this invention. This may be combined with compositions comprisingother agents effective in the treatment of cancer. These compositionswould be provided in a combined amount effective to kill or inhibitproliferation of the cells. This process may involve contacting thecells with platinum(II) complexes of this invention and the agent(s) orfactor(s) at the same time. This may be achieved by contacting the cellswith a single composition or pharmacological formulation that includesboth agents, or by contacting the cells with two distinct compositionsor formulations at the same time, wherein one composition includes oneor more platinum(II) complex of this invention and the other includesthe second agent.

Alternatively, the therapy with the platinum(II) complexes of thisinvention can precede or follow treatment with the other agent byintervals ranging from minutes to weeks. In embodiments where the otheragent and the platinum(II) complexes of this invention are appliedseparately to the cells, one would generally ensure that a significantperiod of time did not expire between the time of each delivery, suchthat the agent and the platinum(II) complexes of this invention wouldstill be able to exert an advantageously combined effect on the cell. Insuch instances, one would contact the cells with both modalities withinabout 12-24 hours of each other and, more preferably, within about 6-12hours of each other, with a delay time of only about 12 hours being mostpreferred. In some situations, it may be desirable to extend the timeperiod for treatment significantly, however, where several days (2, 3,4, 5, 6, or 7 days) to several weeks (1, 2, 3, 4, 5, 6, 7, or 8 weeks)lapse between the respective administrations.

Administration of the therapeutic platinum(II) complexes of the presentinvention to a patient follow general protocols for the administrationof chemotherapeutics, taking into account the toxicity, if any, of theplatinum(II) complexes. Treatment cycles can be repeated as necessary.Various standard therapies, as well as surgical intervention, can beapplied in combination with the described therapy.

Where clinical application of a particular therapy is contemplated, itis necessary to prepare the complex as a pharmaceutical compositionappropriate for the intended application. Generally this entailspreparing a pharmaceutical composition that is essentially free ofpyrogens, as well as any other impurities that could be harmful tohumans or animals. It is also generally desirable to employ appropriatesalts and buffers to render the complex stable and allow for complexuptake by target cells.

Aqueous compositions of the present invention comprise an effectiveamount of the compound, dissolved or dispersed in a pharmaceuticallyacceptable carrier or aqueous medium. Such compositions can also bereferred to as inocula. The phrases “pharmaceutically orpharmacologically acceptable” refer to molecular entities andcompositions that do not produce an adverse, allergic or other untowardreaction when administered to an animal, or a human, as appropriate. Asused herein, “pharmaceutically acceptable carrier” includes any and allsolvents, dispersion media, coatings, antibacterial and antifungalagents, isotonic and absorption delaying agents, and the like. The useof such media and agents for pharmaceutical active substances is wellknown in the art. Except insofar as any conventional media or agent isincompatible with the active ingredient, its use in the therapeuticcompositions is contemplated. Supplementary active ingredients also canbe incorporated into the compositions.

The compositions of the present invention may include classicpharmaceutical preparations. Dispersions also can be prepared inglycerol, liquid polyethylene glycols, and mixtures thereof, and inoils. Under ordinary conditions of storage and use, these preparationscontain a preservative to prevent the growth of microorganisms.

Depending on the particular cancer to be treated, administration oftherapeutic compositions according to the present invention can be viaany common route as long as the target tissue is available via thatroute. This includes oral, nasal, buccal, rectal, vaginal or topical.Topical administration would be particularly advantageous for treatmentof skin cancers. Alternatively, administration can be by orthotopic,intradermal, subcutaneous, intramuscular, intraperitoneal or intravenousinjection. Such compositions can normally be administered aspharmaceutically acceptable compositions that include physiologicallyacceptable carriers, buffers, or other excipients.

The treatments can include various “unit doses.” Unit dose is defined ascontaining a predetermined quantity of the therapeutic compositioncalculated to produce the desired responses in association with itsadministration, ie., the appropriate route and treatment regimen. Thequantity to be administered, and the particular route and formulation,are within the skill of those in the clinical arts. Also of import isthe subject to be treated, in particular, the state of the subject andthe protection desired. A unit dose need not be administered as a singleinjection or administration, but may comprise continuous infusion over aset period of time.

Preferably, patients have adequate bone marrow function (defined as aperipheral absolute granulocyte count of >2,000/mm³ and a platelet countof 100,000/mm³), adequate liver function (bilirubin <1.5 mg/dl), andadequate renal function (creatinine <1.5 mg/dl).

One of the preferred embodiments of the present invention involves theuse of the platinum(II) complexes of this invention to treat cancercells. Target cancer cells include, but are not limited to, cancers ofthe lung, brain, prostate, kidney, liver, ovary, endometrium, breast,skin, stomach, esophagus, head and neck, testicles, germ cancer,epithelial, colon, small intestine, thyroid, cervix, pancreas,glioblastoma, astrocytoma, oligodendroglioma, ependymomas,neurofibrosarcoma, meningia, lymphatic system, and blood. Of particularinterest are non-small cell lung carcinomas including squamous cellcarcinomas, adenocarcinomas, and large cell undifferentiated carcinomas.

According to the present invention, one can treat the cancer by directlyinjecting a tumor with the therapeutic compositions of the presentinvention. Alternatively, the tumor can be infused or perfused with thetherapeutic composition using any suitable delivery vehicle. Local orregional administration, with respect to the tumor, is alsocontemplated. Finally, systemic administration can be performed. Incertain embodiments, the contacting comprises delivering the therapeuticcomposition endoscopically, intratracheally, intralesionally,percutaneously, intravenously, subcutaneously, or intratumorally to thesubject.

Continuous administration can also be applied where appropriate, forexample, where a tumor is excised and the tumor bed is treated toeliminate residual, microscopic disease. Delivery via syringe orcatherization is also contemplated. Such continuous perfusion can takeplace for a period from about 1-2 hours, about 2-6 hours, about 6-12hours, about 12-24 hours, about 1-2 days, about 1-2 weeks or longer,following the initiation of treatment. Generally, the dose of thetherapeutic composition via continuous perfusion is equivalent to thatgiven by a single or multiple injections, adjusted over a period of timeduring which the perfusion occurs.

For tumors of >4 cm, the volume to be administered is be about 4-10 mL(preferably about 10 mL), while for tumors of <4 cm, a volume of about1-3 mL is used (preferably about 3 mL). Multiple injections delivered assingle dose comprise about 0.1 to about 0.5 mL volumes. The tumor mayadvantageously be contacted by administering the therapeutic compositionin multiple injections to the tumor, spaced at approximately 1 cmintervals.

In certain embodiments, the tumor being treated may not, at leastinitially, be resectable. Treatments with therapeutic composition mayincrease the resectability of the tumor due to shrinkage at the marginsor by elimination of certain particularly invasive portions. Followingtreatments, resection may be possible. Additional treatments subsequentto resection will serve to eliminate microscopic residual disease at thetumor site. In certain embodiments, tumor resection may occur prior tothe contacting. The tumor resection may be performed one, two, three ormore times.

A typical course of treatment, for a primary tumor or a post-excisiontumor bed, involves multiple doses. Typical primary tumor treatmentinvolves a 6-dose application over a two-week period. The two-weekregimen may be repeated one, two, three, four, five, six or more times.During a course of treatment, the need to complete the planned dosingsmay be re-evaluated.

Cancer therapies also include a variety of combination therapies withboth chemical and radiation based treatments. Combination chemotherapiesinclude, for example, cisplatin, procarbazine, mechlorethamine,cyclophosphamide, camptothecin, ifosfamide, melphalan, chlorambucil,bisulfan, nitrosurea, dactinomycin, daunorubicin, doxorubicin,bleomycin, plicomycin, mitomycin, etoposide (VP16), tamoxifen, taxol,transplatinum, 5-fluorouracil, vincristin, vinblastin, and methotrexate,or any analog or derivative variant thereof.

Other factors that cause DNA damage and have been used extensivelyinclude what are commonly known as γ-rays, X-rays, and/or the directeddelivery of radioisotopes to tumor cells. Other forms of DNA damagingfactors are also contemplated such as microwaves and UV-irradiation. Itis most likely that all of these factors effect a broad range of damageon DNA, on the precursors of DNA, on the replication and repair of DNA,and on the assembly and maintenance of chromosomes. Dosage ranges forX-rays range from daily doses of 50 to 200 roentgens for prolongedperiods of time (3 to 4 weeks), to single doses of 2000 to 6000roentgens. Dosage ranges for radioisotopes vary widely, and depend onthe half-life of the isotope, the strength and type of radiationemitted, and the uptake by the neoplastic cells.

In addition, gene therapy is becoming increasingly useful for treatingcancers. In such embodiments, expression constructs comprising viralvectors containing the therapeutic genes are used to in order to inducean apoptotic effect in cancer cells. The viral vectors may be adenoviral(see for example, U.S. Pat. Nos. 5,824,544; 5,707,618; 5,693,509;5,670,488; 5,585,362, each incorporated herein by reference), retroviral(see for example, U.S. Pat. Nos. 5,888,502; 5,830,725; 5,770,414;5,686,278; 4,861,719, each incorporated herein by reference), anadeno-associated viral (see for example, U.S. Pat. Nos. 5,474,935;5,139,941; 5,622,856; 5,658,776; 5,773,289; 5,789,390; 5,834,441;5,863,541; 5,851,521; 5,252,479, each incorporated herein by reference),an adenoviral-adenoassociated viral hybrid (see for example, U.S. Pat.No. 5,856,152, incorporated herein by reference) a vaccinia viral or aherpesviral (see for example, U.S. Pat. Nos. 5,879,934; 5,849,571;5,830,727; 5,661,033; 5,328,688, each incorporated herein by reference)vector. These vectors are contacted with the cancer cells to produce thetherapeutic effect. The viral expression construct comprising a nucleicacid encoding a therapeutic anticancer gene can contain any cancertherapy gene known to those of skill in the art including, but notlimited to, p53, p16, p21, MMAC1, p73, zac1, C-CAM, BRCAI, Rb, Bax, Bak,Bim, Bik, Bid, Bad gene, Harakiri, Ad E1B, an ICE-CED3 protease, acytokine such as IL-2, IL-2, IL-3, IL-4, IL-5, IL-6, IL-7, IL-8, IL-9,IL-10, IL-11, IL-12, IL-13, IL-14, IL-15, TNF, GMCSF, β-interferon, andγ-interferon. In other embodiments, the therapeutic nucleic acid may bean antisense nucleic acid directed against an oncogene.

It is understood that the expression vectors comprising the therapeuticgenes to be used in combination with the compositions of the presentinvention will further comprise the appropriate promoters, enhancers,and other regulator elements necessary for efficient replication tooccur. Such elements are well known to those of skill in the art.Exemplary promoters for use herein include, but are not limited to, CMVIE, SV40 IE, RSV, β-actin, tetracycline regulatable, and ecdysoneregulatable. By “treatment,” the present invention refers to any eventthat decreases the growth, kills, or otherwise abrogates the presence ofcancer cells in a subject. Such a treatment can also occur by inhibitionof the metastatic potential or inhibition of tumorigenicity of the cellsso as to achieve a therapeutic outcome.

Various combinations can be employed. For example, where theplatinum(II) complexes of the present invention are represented by “A”and the gene, radiotherapeutic, or chemotherapeutic agent is representedby “B”, combinations can include:

A/B/A B/A/B B/B/A A/A/B A/B/B B/A/A A/B/B/B B/A/B/B B/B/B/A B/B/A/BA/A/B/B A/B/A/B A/B/B/A B/B/A/A B/A/B/A B/A/A/B A/A/A/B B/A/A/A A/B/A/AA/A/B/A

The terms “contacted” and “exposed,” when applied to a cell, are usedherein to describe the process by which a platinum(II) complex of thisinvention and a gene therapeutic construct, a chemotherapeutic, orradiotherapeutic agent are delivered to a target cell or are placed indirect juxtaposition with the target cell. To achieve cell killing orstasis, both agents are delivered to a cell in a combined amounteffective to kill the cell or prevent it from dividing.

The therapeutic compositions of the present invention are advantageouslyadministered in the form of injectable compositions either as liquidsolutions or suspensions, solid forms suitable for solution in, orsuspension in, liquid prior to injection can also be prepared. Thesepreparations also may be emulsified. A typical composition for suchpurpose comprises a pharmaceutically acceptable carrier. For instance,the composition may contain 10 mg, 25 mg, 50 mg or up to about 100 mg ofhuman serum albumin per milliliter of phosphate buffered saline. Otherpharmaceutically acceptable carriers include aqueous solutions,non-toxic excipients, including salts, preservatives, buffers, and thelike. Examples of non-aqueous solvents are propylene glycol,polyethylene glycol, vegetable oil, and injectable organic esters suchas ethyloleate. Aqueous carriers include water, alcoholic/aqueoussolutions, saline solutions, parenteral vehicles such as sodiumchloride, Ringer's dextrose, etc. Intravenous vehicles include fluid andnutrient replenishers. Preservatives include antimicrobial agents,anti-oxidants, chelating agents, and inert gases. The pH and exactconcentration of the various components in the pharmaceuticalcomposition are adjusted according to well known parameters.

Additional formulations are suitable for oral administration. Oralformulations include such typical excipients as, for example,pharmaceutical grades of mannitol, lactose, starch, magnesium stearate,sodium saccharine, cellulose, magnesium carbonate, and the like. Thecompositions take the form of solutions, suspensions, tablets, pills,capsules, sustained release formulations, or powders. When the route istopical, the form can be a cream, ointment, salve or spray.

EXAMPLES

The following examples are included to demonstrate preferred embodimentsof the invention. It should be appreciated by those of skill in the artthat the techniques disclosed in the examples which follow representtechniques discovered by the inventor to function well in the practiceof the invention, and thus can be considered to constitute preferredmodes for its practice. However, those of skill in the art should, inlight of the present disclosure, appreciate that many changes can bemade in the specific embodiments which are disclosed and still obtain alike or similar result without departing from the spirit and scope ofthe invention.

Example 1

Synthesis of the Pt(L-Tyrosine)₂ by a heterogeneous method.

Weigh 83 mg (0.2 mmole) of K₂PtCl₄ and dissolve it in 100 mL deionizedwater. Weigh 72 mg (0.4 mmole) of L-tyrosine and add it to the K₂PtCl₄solution. (Note: L-tyrosine is almost insoluble in water.) Adjust the pHto ca. 8 with sodium hydroxide or sodium bicarbonate. Mix the aliquot atabout 35° C. for 2-4 days. The aliquot gradually becomes a solution andthe color changes from very light tea color to light brown. The UVspectrum shows an additional maximum at about 320 nm. Concentrate thesolution under vacuum. Use a suitable solvent system to re-crystallizethe product by standard technique.

Example 2

Synthesis of Pt(L-alanine)₂ by a homogeneous method.

Weigh 83 mg (0.2 mmole) of K₂PtCl₄ and dissolve it in 100 mL deionizedwater. Weigh 35.6 mg (0.4 mmole) of L-alanine and dissolve it in theK₂PtCl₄ solution. Adjust the pH to ca. 8 with sodium hydroxide or sodiumbicarbonate. Mix the aliquot for 2-4 days at room temperature. Thesolution gradually changes color from light brown to brown. Concentratethe solution under vacuum. Use a suitable solvent system tore-crystallize the product by standard technique.

Example 3

Synthesis of Pt(L-alanine)(L-tyrosine).

Make Pt(L-alanine)Cl₂ according to Example 2 except only half of theL-alanine is required. Add the same number of moles for Pt(L-alanine)Cl₂and L-tyrosine in a suitable amount of water, adjust the pH to ca. 8,and mix it for 2-4 days at room temperature. Proceed as in the previousexample to purify the product.

Example 4

Synthesis of Pt(L-alanine)(phosphatidylserine).

The same method as in Example 3 is used to synthesizePt(L-alanine)(phosphatidylserine).

Example 5

The in-vitro effects of sample #011700 on human squamous carcinoma clonecancer cell line (SCC-1).

Sample #011700 is PtCl₂[CH₃CH(NH)₂COOH]₂ where CH₃CH(NH)₂COOH isalanine.

All cell culture plasticware was purchased from Fisher. Media andantibiotics were purchased from Gibco and Sigma.

Cell viability using a Coulter Counter is used to quantify toxicity.SCC-1 cells are grown in MEM media containing 10% Fetal Bovine Serum,100 units/ml penicillin, 100 μg/ml streptomycin, and 2.5 μg/ml fungizoneat 37° C. in a 5% CO₂ incubator. A 6 well dish is inoculated to 2.0×10⁵cells/well in a total volume of media of 2 ml. Incubation occursovernight and the cells are ready for treatment the next day.

Stock solution of sample #011700 is sterile filtered with a 0.22 μm lowprotein binding syringe filter. Dilutions are made in fresh MEM-10% FBS.

Two days after treatment at 37° C., cells are harvested and quantifiedusing a Coulter Counter. To harvest, all media is removed and 1 ml of1×trypsin solution is added per well. Tryspin is in the well forapproximately 5 minutes at 37° C. After 5 minutes, 1 ml of fresh MEM-10%FBS is added per well. Upon vigorous mixing to ensure breakup ofaggregate cells, dilutions are made in Isoton®II ready for cell counts.Each well is counted twice. Thus, duplicate wells plus duplicate countsyield 4 cell counts per parameter above.

The results shown in the following table indicate that #011700 showsinhibition of the growth of SCC-1 cells in-vitro.

μM #011700 Cell Count/mL 0 5.70 × 10⁵ 20 6.00 × 10⁵ 30 5.80 × 10⁵ 405.20 × 10⁵ 50 4.40 × 10⁵ 60 3.80 × 10⁵

The platinum(II) complexes of this invention may be formulated withcustomary pharmaceutical excipients to make suitable dosage forms bystandard pharmaceutical techniques and processes. Such excipientsinclude, but are not limited to, starch, cellulose, lactose, magnesiumstearate, stearic acid, talc, calcium phosphate, inorganic buffer,organic buffer, surfactant, silicon dioxide, and food color. Twoexamples of the dosage forms are as follows:

Example 6

An example of making an injectable dosage form.

Weigh 50 mg of Pt(L-Tyrosine)₂ and dissolve it in 1000 mL of deionizedwater. A suitable amount of phosphate buffer is added to a bring the pHto about 7.4. The solution is sterilized to make an injectable dosageform.

Example 7

An example of making an oral dosage form.

A pharmaceutical dosage form for oral administration can be made fromthe following formulation using standard pharmaceutical techniques andequipment.

100 mg of Pt(L-alanine)(L-tyrosine)

145 mg of lactose

75 mg microcrystalline cellulose

5 mg magnesium stearate

Example 8

An example of administration of a platinum complex of this invention.

A therapeutically effective amount of a platinum(II) complex of thisinvention is administered to a cancer patient in a suitable dosage form.

In a therapeutic regiment, 10 mg-1000 mg of the platinum(II) complex isadministered to a cancer patient by injection once every 1 to 4 weeks.The regimen can be repeated.

Example 9

An alternate example of administration of a platinum complex of thisinvention.

In a therapeutic regiment, 10 mg-1000 mg of a platinum(II) complex ofthe present invention is administered to a cancer patient orally onceevery 1 to 4 weeks. The regimen can be repeated.

The complexes of the present invention can also be used in the treatmentof AIDS (Acquired Immune Deficiency Syndrome). Because these complexescan hamper the DNA or RNA replication process, they can be effectiveagainst the HIV (Human Immunodeficiency Virus) and may be used for thetreatment of AIDS.

In conclusion, a series of platinum(II) complexes, as carboplatinanalogs, are disclosed in this invention. The complexes can berepresented by cis-Pt(II)L¹L², wherein each of L¹ and L², independentlyis the carboxylate of phosphatidylserine, an α-amino acid, a β-aminoacid, or a derivative thereof, and wherein each ligand is bidentate with—NH₂ and —COO⁻ as the binding sites. The free acids of these complexesare also disclosed. The synthesis and the use of these platinum(II)complexes are presented in this invention.

Although the description above contains many specifics, these should notbe construed as limiting the scope of the invention, but as merelyproviding illustrations of some of the presently preferred embodimentsof this invention. For example, the compounds can be made in pure waterinstead of the mixture of methanol and water.

Thus the scope of this invention should be determined by the appendedclaims and their legal equivalents, rather than by the examples given.

I claim:
 1. A complex with the formula cis-Pt(II)L¹L², wherein each ofL¹ and L², independently, is the carboxylate of phosphatidylserine, thederivative of an α-amino acid, or the derivative of a β-amino acid,wherein each ligand is bidentate with —NH₂ and —COO⁻ as binding sites.2. A complex comprising ligands in free acid form with the formulacis-Pt(II)Cl₂L³L⁴, cis-Pt(II)Br₂L³L⁴ or cis-Pt(II)(NO₃)₂L³L⁴, whereineach of L³ and L⁴, independently is phosphatidylserine, an α-amino acid,a β-amino acid, a derivative of an α-amino acid, or the derivative of aβ-amino acid, wherein each ligand is monodentate with —NH₂ as a bindingsite.